/*
 * QR Code generator library (C)
 *
 * Copyright (c) Project Nayuki. (MIT License)
 * https://www.nayuki.io/page/qr-code-generator-library
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * - The above copyright notice and this permission notice shall be included in
 *   all copies or substantial portions of the Software.
 * - The Software is provided "as is", without warranty of any kind, express or
 *   implied, including but not limited to the warranties of merchantability,
 *   fitness for a particular purpose and noninfringement. In no event shall the
 *   authors or copyright holders be liable for any claim, damages or other
 *   liability, whether in an action of contract, tort or otherwise, arising from,
 *   out of or in connection with the Software or the use or other dealings in the
 *   Software.
 */

#include <assert.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include "qrcodegen.h"

#ifndef QRCODEGEN_TEST
#define testable static  // Keep functions private
#else
// Expose private functions
#ifndef __cplusplus
#define testable
#else
// Needed for const variables because they are treated as implicitly 'static' in C++
#define testable extern
#endif
#endif


/*---- Forward declarations for private functions ----*/

// Regarding all public and private functions defined in this source file:
// - They require all pointer/array arguments to be not null.
// - They only read input scalar/array arguments, write to output pointer/array
//   arguments, and return scalar values; they are "pure" functions.
// - They don't read mutable global variables or write to any global variables.
// - They don't perform I/O, read the clock, print to console, etc.
// - They allocate a small and constant amount of stack memory.
// - They don't allocate or free any memory on the heap.
// - They don't recurse or mutually recurse. All the code
//   could be inlined into the top-level public functions.
// - They run in at most quadratic time with respect to input arguments.
//   Most functions run in linear time, and some in constant time.
//   There are no unbounded loops or non-obvious termination conditions.
// - They are completely thread-safe if the caller does not give the
//   same writable buffer to concurrent calls to these functions.

testable void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen);

testable void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]);
testable int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl);
testable int getNumRawDataModules(int version);

testable void calcReedSolomonGenerator(int degree, uint8_t result[]);
testable void calcReedSolomonRemainder(const uint8_t data[], int dataLen,
                                       const uint8_t generator[], int degree, uint8_t result[]);
testable uint8_t finiteFieldMultiply(uint8_t x, uint8_t y);

testable void initializeFunctionModules(int version, uint8_t qrcode[]);
static void drawWhiteFunctionModules(uint8_t qrcode[], int version);
static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[]);
testable int getAlignmentPatternPositions(int version, uint8_t result[7]);
static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[]);

static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[]);
static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], enum qrcodegen_Mask mask);
static long getPenaltyScore(const uint8_t qrcode[]);

testable bool getModule(const uint8_t qrcode[], int x, int y);
testable void setModule(uint8_t qrcode[], int x, int y, bool isBlack);
testable void setModuleBounded(uint8_t qrcode[], int x, int y, bool isBlack);
static bool getBit(int x, int i);

testable int calcSegmentBitLength(enum qrcodegen_Mode mode, size_t numChars);
testable int getTotalBits(const struct qrcodegen_Segment segs[], size_t len, int version);
static int numCharCountBits(enum qrcodegen_Mode mode, int version);



/*---- Private tables of constants ----*/

// For checking text and encoding segments.
static const char *ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";

// For generating error correction codes.
testable const int8_t ECC_CODEWORDS_PER_BLOCK[4][41] = {
    // Version: (note that index 0 is for padding, and is set to an illegal value)
    //0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level
    { -1,  7, 10, 15, 20, 26, 18, 20, 24, 30, 18, 20, 24, 26, 30, 22, 24, 28, 30, 28, 28, 28, 28, 30, 30, 26, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // Low
    { -1, 10, 16, 26, 18, 24, 16, 18, 22, 22, 26, 30, 22, 22, 24, 24, 28, 28, 26, 26, 26, 26, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28}, // Medium
    { -1, 13, 22, 18, 26, 18, 24, 18, 22, 20, 24, 28, 26, 24, 20, 30, 24, 28, 28, 26, 30, 28, 30, 30, 30, 30, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // Quartile
    { -1, 17, 28, 22, 16, 22, 28, 26, 26, 24, 28, 24, 28, 22, 24, 24, 30, 28, 28, 26, 28, 30, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // High
};

// For generating error correction codes.
testable const int8_t NUM_ERROR_CORRECTION_BLOCKS[4][41] = {
    // Version: (note that index 0 is for padding, and is set to an illegal value)
    //0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level
    { -1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 4,  4,  4,  4,  4,  6,  6,  6,  6,  7,  8,  8,  9,  9, 10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25}, // Low
    { -1, 1, 1, 1, 2, 2, 4, 4, 4, 5, 5,  5,  8,  9,  9, 10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49}, // Medium
    { -1, 1, 1, 2, 2, 4, 4, 6, 6, 8, 8,  8, 10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68}, // Quartile
    { -1, 1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81}, // High
};

// For automatic mask pattern selection.
static const int PENALTY_N1 = 3;
static const int PENALTY_N2 = 3;
static const int PENALTY_N3 = 40;
static const int PENALTY_N4 = 10;



/*---- High-level QR Code encoding functions ----*/

// Public function - see documentation comment in header file.
bool qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[],
                          enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl)
{

    size_t textLen = strlen(text);
    if (textLen == 0) {
        return qrcodegen_encodeSegmentsAdvanced(NULL, 0, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode);
    }
    size_t bufLen = qrcodegen_BUFFER_LEN_FOR_VERSION(maxVersion);

    struct qrcodegen_Segment seg;
    if (qrcodegen_isNumeric(text)) {
        if (qrcodegen_calcSegmentBufferSize(qrcodegen_Mode_NUMERIC, textLen) > bufLen) {
            goto fail;
        }
        seg = qrcodegen_makeNumeric(text, tempBuffer);
    } else if (qrcodegen_isAlphanumeric(text)) {
        if (qrcodegen_calcSegmentBufferSize(qrcodegen_Mode_ALPHANUMERIC, textLen) > bufLen) {
            goto fail;
        }
        seg = qrcodegen_makeAlphanumeric(text, tempBuffer);
    } else {
        if (textLen > bufLen) {
            goto fail;
        }
        for (size_t i = 0; i < textLen; i++) {
            tempBuffer[i] = (uint8_t)text[i];
        }
        seg.mode = qrcodegen_Mode_BYTE;
        seg.bitLength = calcSegmentBitLength(seg.mode, textLen);
        if (seg.bitLength == -1) {
            goto fail;
        }
        seg.numChars = (int)textLen;
        seg.data = tempBuffer;
    }
    return qrcodegen_encodeSegmentsAdvanced(&seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode);

fail:
    qrcode[0] = 0;  // Set size to invalid value for safety
    return false;
}


// Public function - see documentation comment in header file.
bool qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode[],
                            enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl)
{

    struct qrcodegen_Segment seg;
    seg.mode = qrcodegen_Mode_BYTE;
    seg.bitLength = calcSegmentBitLength(seg.mode, dataLen);
    if (seg.bitLength == -1) {
        qrcode[0] = 0;  // Set size to invalid value for safety
        return false;
    }
    seg.numChars = (int)dataLen;
    seg.data = dataAndTemp;
    return qrcodegen_encodeSegmentsAdvanced(&seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, dataAndTemp, qrcode);
}


// Appends the given sequence of bits to the given byte-based bit buffer, increasing the bit length.
testable void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen)
{
    assert(0 <= numBits && numBits <= 16 && (unsigned long)val >> numBits == 0);
    for (int i = numBits - 1; i >= 0; i--, (*bitLen)++) {
        buffer[*bitLen >> 3] |= ((val >> i) & 1) << (7 - (*bitLen & 7));
    }
}



/*---- Error correction code generation functions ----*/

// Appends error correction bytes to each block of the given data array, then interleaves bytes
// from the blocks and stores them in the result array. data[0 : rawCodewords - totalEcc] contains
// the input data. data[rawCodewords - totalEcc : rawCodewords] is used as a temporary work area
// and will be clobbered by this function. The final answer is stored in result[0 : rawCodewords].
testable void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[])
{
    // Calculate parameter numbers
    assert(0 <= (int)ecl && (int)ecl < 4 && qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
    int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[(int)ecl][version];
    int blockEccLen = ECC_CODEWORDS_PER_BLOCK[(int)ecl][version];
    int rawCodewords = getNumRawDataModules(version) / 8;
    int dataLen = rawCodewords - blockEccLen * numBlocks;
    int numShortBlocks = numBlocks - rawCodewords % numBlocks;
    int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen;

    // Split data into blocks and append ECC after all data
    uint8_t generator[30];
    calcReedSolomonGenerator(blockEccLen, generator);
    for (int i = 0, j = dataLen, k = 0; i < numBlocks; i++) {
        int blockLen = shortBlockDataLen;
        if (i >= numShortBlocks) {
            blockLen++;
        }
        calcReedSolomonRemainder(&data[k], blockLen, generator, blockEccLen, &data[j]);
        j += blockEccLen;
        k += blockLen;
    }

    // Interleave (not concatenate) the bytes from every block into a single sequence
    for (int i = 0, k = 0; i < numBlocks; i++) {
        for (int j = 0, l = i; j < shortBlockDataLen; j++, k++, l += numBlocks) {
            result[l] = data[k];
        }
        if (i >= numShortBlocks) {
            k++;
        }
    }
    for (int i = numShortBlocks, k = (numShortBlocks + 1) * shortBlockDataLen, l = numBlocks * shortBlockDataLen;
         i < numBlocks; i++, k += shortBlockDataLen + 1, l++) {
        result[l] = data[k];
    }
    for (int i = 0, k = dataLen; i < numBlocks; i++) {
        for (int j = 0, l = dataLen + i; j < blockEccLen; j++, k++, l += numBlocks) {
            result[l] = data[k];
        }
    }
}


// Returns the number of 8-bit codewords that can be used for storing data (not ECC),
// for the given version number and error correction level. The result is in the range [9, 2956].
testable int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl)
{
    int v = version, e = (int)ecl;
    assert(0 <= e && e < 4 && qrcodegen_VERSION_MIN <= v && v <= qrcodegen_VERSION_MAX);
    return getNumRawDataModules(v) / 8 - ECC_CODEWORDS_PER_BLOCK[e][v] * NUM_ERROR_CORRECTION_BLOCKS[e][v];
}


// Returns the number of data bits that can be stored in a QR Code of the given version number, after
// all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
// The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table.
testable int getNumRawDataModules(int version)
{
    assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
    int result = (16 * version + 128) * version + 64;
    if (version >= 2) {
        int numAlign = version / 7 + 2;
        result -= (25 * numAlign - 10) * numAlign - 55;
        if (version >= 7) {
            result -= 18 * 2;    // Subtract version information
        }
    }
    return result;
}



/*---- Reed-Solomon ECC generator functions ----*/

// Calculates the Reed-Solomon generator polynomial of the given degree, storing in result[0 : degree].
testable void calcReedSolomonGenerator(int degree, uint8_t result[])
{
    // Start with the monomial x^0
    assert(1 <= degree && degree <= 30);
    memset(result, 0, degree * sizeof(result[0]));
    result[degree - 1] = 1;

    // Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
    // drop the highest term, and store the rest of the coefficients in order of descending powers.
    // Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
    uint8_t root = 1;
    for (int i = 0; i < degree; i++) {
        // Multiply the current product by (x - r^i)
        for (int j = 0; j < degree; j++) {
            result[j] = finiteFieldMultiply(result[j], root);
            if (j + 1 < degree) {
                result[j] ^= result[j + 1];
            }
        }
        root = finiteFieldMultiply(root, 0x02);
    }
}


// Calculates the remainder of the polynomial data[0 : dataLen] when divided by the generator[0 : degree], where all
// polynomials are in big endian and the generator has an implicit leading 1 term, storing the result in result[0 : degree].
testable void calcReedSolomonRemainder(const uint8_t data[], int dataLen,
                                       const uint8_t generator[], int degree, uint8_t result[])
{

    // Perform polynomial division
    assert(1 <= degree && degree <= 30);
    memset(result, 0, degree * sizeof(result[0]));
    for (int i = 0; i < dataLen; i++) {
        uint8_t factor = data[i] ^ result[0];
        memmove(&result[0], &result[1], (degree - 1) * sizeof(result[0]));
        result[degree - 1] = 0;
        for (int j = 0; j < degree; j++) {
            result[j] ^= finiteFieldMultiply(generator[j], factor);
        }
    }
}


// Returns the product of the two given field elements modulo GF(2^8/0x11D).
// All inputs are valid. This could be implemented as a 256*256 lookup table.
testable uint8_t finiteFieldMultiply(uint8_t x, uint8_t y)
{
    // Russian peasant multiplication
    uint8_t z = 0;
    for (int i = 7; i >= 0; i--) {
        z = (z << 1) ^ ((z >> 7) * 0x11D);
        z ^= ((y >> i) & 1) * x;
    }
    return z;
}



/*---- Drawing function modules ----*/

// Clears the given QR Code grid with white modules for the given
// version's size, then marks every function module as black.
testable void initializeFunctionModules(int version, uint8_t qrcode[])
{
    // Initialize QR Code
    int qrsize = version * 4 + 17;
    memset(qrcode, 0, ((qrsize * qrsize + 7) / 8 + 1) * sizeof(qrcode[0]));
    qrcode[0] = (uint8_t)qrsize;

    // Fill horizontal and vertical timing patterns
    fillRectangle(6, 0, 1, qrsize, qrcode);
    fillRectangle(0, 6, qrsize, 1, qrcode);

    // Fill 3 finder patterns (all corners except bottom right) and format bits
    fillRectangle(0, 0, 9, 9, qrcode);
    fillRectangle(qrsize - 8, 0, 8, 9, qrcode);
    fillRectangle(0, qrsize - 8, 9, 8, qrcode);

    // Fill numerous alignment patterns
    uint8_t alignPatPos[7] = {0};
    int numAlign = getAlignmentPatternPositions(version, alignPatPos);
    for (int i = 0; i < numAlign; i++) {
        for (int j = 0; j < numAlign; j++) {
            if ((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0)) {
                continue;    // Skip the three finder corners
            } else {
                fillRectangle(alignPatPos[i] - 2, alignPatPos[j] - 2, 5, 5, qrcode);
            }
        }
    }

    // Fill version blocks
    if (version >= 7) {
        fillRectangle(qrsize - 11, 0, 3, 6, qrcode);
        fillRectangle(0, qrsize - 11, 6, 3, qrcode);
    }
}


// Draws white function modules and possibly some black modules onto the given QR Code, without changing
// non-function modules. This does not draw the format bits. This requires all function modules to be previously
// marked black (namely by initializeFunctionModules()), because this may skip redrawing black function modules.
static void drawWhiteFunctionModules(uint8_t qrcode[], int version)
{
    // Draw horizontal and vertical timing patterns
    int qrsize = qrcodegen_getSize(qrcode);
    for (int i = 7; i < qrsize - 7; i += 2) {
        setModule(qrcode, 6, i, false);
        setModule(qrcode, i, 6, false);
    }

    // Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
    for (int i = -4; i <= 4; i++) {
        for (int j = -4; j <= 4; j++) {
            int dist = abs(i);
            if (abs(j) > dist) {
                dist = abs(j);
            }
            if (dist == 2 || dist == 4) {
                setModuleBounded(qrcode, 3 + j, 3 + i, false);
                setModuleBounded(qrcode, qrsize - 4 + j, 3 + i, false);
                setModuleBounded(qrcode, 3 + j, qrsize - 4 + i, false);
            }
        }
    }

    // Draw numerous alignment patterns
    uint8_t alignPatPos[7] = {0};
    int numAlign = getAlignmentPatternPositions(version, alignPatPos);
    for (int i = 0; i < numAlign; i++) {
        for (int j = 0; j < numAlign; j++) {
            if ((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0)) {
                continue;    // Skip the three finder corners
            } else {
                for (int k = -1; k <= 1; k++) {
                    for (int l = -1; l <= 1; l++) {
                        setModule(qrcode, alignPatPos[i] + l, alignPatPos[j] + k, k == 0 && l == 0);
                    }
                }
            }
        }
    }

    // Draw version blocks
    if (version >= 7) {
        // Calculate error correction code and pack bits
        int rem = version;  // version is uint6, in the range [7, 40]
        for (int i = 0; i < 12; i++) {
            rem = (rem << 1) ^ ((rem >> 11) * 0x1F25);
        }
        long data = (long)version << 12 | rem;  // uint18
        assert(data >> 18 == 0);

        // Draw two copies
        for (int i = 0; i < 6; i++) {
            for (int j = 0; j < 3; j++) {
                int k = qrsize - 11 + j;
                setModule(qrcode, k, i, (data & 1) != 0);
                setModule(qrcode, i, k, (data & 1) != 0);
                data >>= 1;
            }
        }
    }
}


// Draws two copies of the format bits (with its own error correction code) based
// on the given mask and error correction level. This always draws all modules of
// the format bits, unlike drawWhiteFunctionModules() which might skip black modules.
static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[])
{
    // Calculate error correction code and pack bits
    assert(0 <= (int)mask && (int)mask <= 7);
    int data = -1;  // Dummy value
    switch (ecl) {
        case qrcodegen_Ecc_LOW     :
            data = 1;
            break;
        case qrcodegen_Ecc_MEDIUM  :
            data = 0;
            break;
        case qrcodegen_Ecc_QUARTILE:
            data = 3;
            break;
        case qrcodegen_Ecc_HIGH    :
            data = 2;
            break;
        default:
            assert(false);
    }
    data = data << 3 | (int)mask;  // ecl-derived value is uint2, mask is uint3
    int rem = data;
    for (int i = 0; i < 10; i++) {
        rem = (rem << 1) ^ ((rem >> 9) * 0x537);
    }
    data = data << 10 | rem;
    data ^= 0x5412;  // uint15
    assert(data >> 15 == 0);

    // Draw first copy
    for (int i = 0; i <= 5; i++) {
        setModule(qrcode, 8, i, getBit(data, i));
    }
    setModule(qrcode, 8, 7, getBit(data, 6));
    setModule(qrcode, 8, 8, getBit(data, 7));
    setModule(qrcode, 7, 8, getBit(data, 8));
    for (int i = 9; i < 15; i++) {
        setModule(qrcode, 14 - i, 8, getBit(data, i));
    }

    // Draw second copy
    int qrsize = qrcodegen_getSize(qrcode);
    for (int i = 0; i <= 7; i++) {
        setModule(qrcode, qrsize - 1 - i, 8, getBit(data, i));
    }
    for (int i = 8; i < 15; i++) {
        setModule(qrcode, 8, qrsize - 15 + i, getBit(data, i));
    }
    setModule(qrcode, 8, qrsize - 8, true);
}


// Calculates the positions of alignment patterns in ascending order for the given version number,
// storing them to the given array and returning an array length in the range [0, 7].
testable int getAlignmentPatternPositions(int version, uint8_t result[7])
{
    if (version == 1) {
        return 0;
    }
    int numAlign = version / 7 + 2;
    int step;
    if (version != 32) {
        // ceil((size - 13) / (2*numAlign - 2)) * 2
        step = (version * 4 + numAlign * 2 + 1) / (2 * numAlign - 2) * 2;
    } else { // C-C-C-Combo breaker!
        step = 26;
    }
    for (int i = numAlign - 1, pos = version * 4 + 10; i >= 1; i--, pos -= step) {
        result[i] = pos;
    }
    result[0] = 6;
    return numAlign;
}


// Sets every pixel in the range [left : left + width] * [top : top + height] to black.
static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[])
{
    for (int dy = 0; dy < height; dy++) {
        for (int dx = 0; dx < width; dx++) {
            setModule(qrcode, left + dx, top + dy, true);
        }
    }
}



/*---- Drawing data modules and masking ----*/

// Draws the raw codewords (including data and ECC) onto the given QR Code. This requires the initial state of
// the QR Code to be black at function modules and white at codeword modules (including unused remainder bits).
static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[])
{
    int qrsize = qrcodegen_getSize(qrcode);
    int i = 0;  // Bit index into the data
    // Do the funny zigzag scan
    for (int right = qrsize - 1; right >= 1; right -= 2) {  // Index of right column in each column pair
        if (right == 6) {
            right = 5;
        }
        for (int vert = 0; vert < qrsize; vert++) {  // Vertical counter
            for (int j = 0; j < 2; j++) {
                int x = right - j;  // Actual x coordinate
                bool upward = ((right + 1) & 2) == 0;
                int y = upward ? qrsize - 1 - vert : vert;  // Actual y coordinate
                if (!getModule(qrcode, x, y) && i < dataLen * 8) {
                    bool black = getBit(data[i >> 3], 7 - (i & 7));
                    setModule(qrcode, x, y, black);
                    i++;
                }
                // If there are any remainder bits (0 to 7), they are already
                // set to 0/false/white when the grid of modules was initialized
            }
        }
    }
    assert(i == dataLen * 8);
}


// XORs the data modules in this QR Code with the given mask pattern. Due to XOR's mathematical
// properties, calling applyMask(..., m) twice with the same value is equivalent to no change at all.
// This means it is possible to apply a mask, undo it, and try another mask. Note that a final
// well-formed QR Code symbol needs exactly one mask applied (not zero, not two, etc.).
static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], enum qrcodegen_Mask mask)
{
    assert(0 <= (int)mask && (int)mask <= 7);  // Disallows qrcodegen_Mask_AUTO
    int qrsize = qrcodegen_getSize(qrcode);
    for (int y = 0; y < qrsize; y++) {
        for (int x = 0; x < qrsize; x++) {
            if (getModule(functionModules, x, y)) {
                continue;
            }
            bool invert = false;  // Dummy value
            switch ((int)mask) {
                case 0:
                    invert = (x + y) % 2 == 0;
                    break;
                case 1:
                    invert = y % 2 == 0;
                    break;
                case 2:
                    invert = x % 3 == 0;
                    break;
                case 3:
                    invert = (x + y) % 3 == 0;
                    break;
                case 4:
                    invert = (x / 3 + y / 2) % 2 == 0;
                    break;
                case 5:
                    invert = x * y % 2 + x * y % 3 == 0;
                    break;
                case 6:
                    invert = (x * y % 2 + x * y % 3) % 2 == 0;
                    break;
                case 7:
                    invert = ((x + y) % 2 + x * y % 3) % 2 == 0;
                    break;
                default:
                    assert(false);
            }
            bool val = getModule(qrcode, x, y);
            setModule(qrcode, x, y, val ^ invert);
        }
    }
}


// Calculates and returns the penalty score based on state of the given QR Code's current modules.
// This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
static long getPenaltyScore(const uint8_t qrcode[])
{
    int qrsize = qrcodegen_getSize(qrcode);
    long result = 0;

    // Adjacent modules in row having same color
    for (int y = 0; y < qrsize; y++) {
        bool colorX = false;
        for (int x = 0, runX = -1; x < qrsize; x++) {
            if (x == 0 || getModule(qrcode, x, y) != colorX) {
                colorX = getModule(qrcode, x, y);
                runX = 1;
            } else {
                runX++;
                if (runX == 5) {
                    result += PENALTY_N1;
                } else if (runX > 5) {
                    result++;
                }
            }
        }
    }
    // Adjacent modules in column having same color
    for (int x = 0; x < qrsize; x++) {
        bool colorY = false;
        for (int y = 0, runY = -1; y < qrsize; y++) {
            if (y == 0 || getModule(qrcode, x, y) != colorY) {
                colorY = getModule(qrcode, x, y);
                runY = 1;
            } else {
                runY++;
                if (runY == 5) {
                    result += PENALTY_N1;
                } else if (runY > 5) {
                    result++;
                }
            }
        }
    }

    // 2*2 blocks of modules having same color
    for (int y = 0; y < qrsize - 1; y++) {
        for (int x = 0; x < qrsize - 1; x++) {
            bool  color = getModule(qrcode, x, y);
            if (  color == getModule(qrcode, x + 1, y) &&
                  color == getModule(qrcode, x, y + 1) &&
                  color == getModule(qrcode, x + 1, y + 1)) {
                result += PENALTY_N2;
            }
        }
    }

    // Finder-like pattern in rows
    for (int y = 0; y < qrsize; y++) {
        for (int x = 0, bits = 0; x < qrsize; x++) {
            bits = ((bits << 1) & 0x7FF) | (getModule(qrcode, x, y) ? 1 : 0);
            if (x >= 10 && (bits == 0x05D || bits == 0x5D0)) { // Needs 11 bits accumulated
                result += PENALTY_N3;
            }
        }
    }
    // Finder-like pattern in columns
    for (int x = 0; x < qrsize; x++) {
        for (int y = 0, bits = 0; y < qrsize; y++) {
            bits = ((bits << 1) & 0x7FF) | (getModule(qrcode, x, y) ? 1 : 0);
            if (y >= 10 && (bits == 0x05D || bits == 0x5D0)) { // Needs 11 bits accumulated
                result += PENALTY_N3;
            }
        }
    }

    // Balance of black and white modules
    int black = 0;
    for (int y = 0; y < qrsize; y++) {
        for (int x = 0; x < qrsize; x++) {
            if (getModule(qrcode, x, y)) {
                black++;
            }
        }
    }
    int total = qrsize * qrsize;
    // Find smallest k such that (45-5k)% <= dark/total <= (55+5k)%
    for (int k = 0; black * 20L < (9L - k)*total || black * 20L > (11L + k)*total; k++) {
        result += PENALTY_N4;
    }
    return result;
}



/*---- Basic QR Code information ----*/

// Public function - see documentation comment in header file.
int qrcodegen_getSize(const uint8_t qrcode[])
{
    assert(qrcode != NULL);
    int result = qrcode[0];
    assert((qrcodegen_VERSION_MIN * 4 + 17) <= result
           && result <= (qrcodegen_VERSION_MAX * 4 + 17));
    return result;
}


// Public function - see documentation comment in header file.
bool qrcodegen_getModule(const uint8_t qrcode[], int x, int y)
{
    assert(qrcode != NULL);
    int qrsize = qrcode[0];
    return (0 <= x && x < qrsize && 0 <= y && y < qrsize) && getModule(qrcode, x, y);
}


// Gets the module at the given coordinates, which must be in bounds.
testable bool getModule(const uint8_t qrcode[], int x, int y)
{
    int qrsize = qrcode[0];
    assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
    int index = y * qrsize + x;
    return getBit(qrcode[(index >> 3) + 1], index & 7);
}


// Sets the module at the given coordinates, which must be in bounds.
testable void setModule(uint8_t qrcode[], int x, int y, bool isBlack)
{
    int qrsize = qrcode[0];
    assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
    int index = y * qrsize + x;
    int bitIndex = index & 7;
    int byteIndex = (index >> 3) + 1;
    if (isBlack) {
        qrcode[byteIndex] |= 1 << bitIndex;
    } else {
        qrcode[byteIndex] &= (1 << bitIndex) ^ 0xFF;
    }
}


// Sets the module at the given coordinates, doing nothing if out of bounds.
testable void setModuleBounded(uint8_t qrcode[], int x, int y, bool isBlack)
{
    int qrsize = qrcode[0];
    if (0 <= x && x < qrsize && 0 <= y && y < qrsize) {
        setModule(qrcode, x, y, isBlack);
    }
}


// Returns true iff the i'th bit of x is set to 1.
static bool getBit(int x, int i)
{
    return ((x >> i) & 1) != 0;
}



/*---- Segment handling ----*/

// Public function - see documentation comment in header file.
bool qrcodegen_isAlphanumeric(const char *text)
{
    assert(text != NULL);
    for (; *text != '\0'; text++) {
        if (strchr(ALPHANUMERIC_CHARSET, *text) == NULL) {
            return false;
        }
    }
    return true;
}


// Public function - see documentation comment in header file.
bool qrcodegen_isNumeric(const char *text)
{
    assert(text != NULL);
    for (; *text != '\0'; text++) {
        if (*text < '0' || *text > '9') {
            return false;
        }
    }
    return true;
}


// Public function - see documentation comment in header file.
size_t qrcodegen_calcSegmentBufferSize(enum qrcodegen_Mode mode, size_t numChars)
{
    int temp = calcSegmentBitLength(mode, numChars);
    if (temp == -1) {
        return SIZE_MAX;
    }
    assert(0 <= temp && temp <= INT16_MAX);
    return ((size_t)temp + 7) / 8;
}


// Returns the number of data bits needed to represent a segment
// containing the given number of characters using the given mode. Notes:
// - Returns -1 on failure, i.e. numChars > INT16_MAX or
//   the number of needed bits exceeds INT16_MAX (i.e. 32767).
// - Otherwise, all valid results are in the range [0, INT16_MAX].
// - For byte mode, numChars measures the number of bytes, not Unicode code points.
// - For ECI mode, numChars must be 0, and the worst-case number of bits is returned.
//   An actual ECI segment can have shorter data. For non-ECI modes, the result is exact.
testable int calcSegmentBitLength(enum qrcodegen_Mode mode, size_t numChars)
{
    const int LIMIT = INT16_MAX;  // Can be configured as high as INT_MAX
    if (numChars > (unsigned int)LIMIT) {
        return -1;
    }
    int n = (int)numChars;

    int result = -2;
    if (mode == qrcodegen_Mode_NUMERIC) {
        // n * 3 + ceil(n / 3)
        if (n > LIMIT / 3) {
            goto overflow;
        }
        result = n * 3;
        int temp = n / 3 + (n % 3 == 0 ? 0 : 1);
        if (temp > LIMIT - result) {
            goto overflow;
        }
        result += temp;
    } else if (mode == qrcodegen_Mode_ALPHANUMERIC) {
        // n * 5 + ceil(n / 2)
        if (n > LIMIT / 5) {
            goto overflow;
        }
        result = n * 5;
        int temp = n / 2 + n % 2;
        if (temp > LIMIT - result) {
            goto overflow;
        }
        result += temp;
    } else if (mode == qrcodegen_Mode_BYTE) {
        if (n > LIMIT / 8) {
            goto overflow;
        }
        result = n * 8;
    } else if (mode == qrcodegen_Mode_KANJI) {
        if (n > LIMIT / 13) {
            goto overflow;
        }
        result = n * 13;
    } else if (mode == qrcodegen_Mode_ECI && numChars == 0) {
        result = 3 * 8;
    }
    assert(0 <= result && result <= LIMIT);
    return result;
overflow:
    return -1;
}


// Public function - see documentation comment in header file.
struct qrcodegen_Segment qrcodegen_makeBytes(const uint8_t data[], size_t len, uint8_t buf[])
{
    assert(data != NULL || len == 0);
    struct qrcodegen_Segment result;
    result.mode = qrcodegen_Mode_BYTE;
    result.bitLength = calcSegmentBitLength(result.mode, len);
    assert(result.bitLength != -1);
    result.numChars = (int)len;
    if (len > 0) {
        memcpy(buf, data, len * sizeof(buf[0]));
    }
    result.data = buf;
    return result;
}


// Public function - see documentation comment in header file.
struct qrcodegen_Segment qrcodegen_makeNumeric(const char *digits, uint8_t buf[])
{
    assert(digits != NULL);
    struct qrcodegen_Segment result;
    size_t len = strlen(digits);
    result.mode = qrcodegen_Mode_NUMERIC;
    int bitLen = calcSegmentBitLength(result.mode, len);
    assert(bitLen != -1);
    result.numChars = (int)len;
    if (bitLen > 0) {
        memset(buf, 0, ((size_t)bitLen + 7) / 8 * sizeof(buf[0]));
    }
    result.bitLength = 0;

    unsigned int accumData = 0;
    int accumCount = 0;
    for (; *digits != '\0'; digits++) {
        char c = *digits;
        assert('0' <= c && c <= '9');
        accumData = accumData * 10 + (c - '0');
        accumCount++;
        if (accumCount == 3) {
            appendBitsToBuffer(accumData, 10, buf, &result.bitLength);
            accumData = 0;
            accumCount = 0;
        }
    }
    if (accumCount > 0) { // 1 or 2 digits remaining
        appendBitsToBuffer(accumData, accumCount * 3 + 1, buf, &result.bitLength);
    }
    assert(result.bitLength == bitLen);
    result.data = buf;
    return result;
}


// Public function - see documentation comment in header file.
struct qrcodegen_Segment qrcodegen_makeAlphanumeric(const char *text, uint8_t buf[])
{
    assert(text != NULL);
    struct qrcodegen_Segment result;
    size_t len = strlen(text);
    result.mode = qrcodegen_Mode_ALPHANUMERIC;
    int bitLen = calcSegmentBitLength(result.mode, len);
    assert(bitLen != -1);
    result.numChars = (int)len;
    if (bitLen > 0) {
        memset(buf, 0, ((size_t)bitLen + 7) / 8 * sizeof(buf[0]));
    }
    result.bitLength = 0;

    unsigned int accumData = 0;
    int accumCount = 0;
    for (; *text != '\0'; text++) {
        const char *temp = strchr(ALPHANUMERIC_CHARSET, *text);
        assert(temp != NULL);
        accumData = accumData * 45 + (temp - ALPHANUMERIC_CHARSET);
        accumCount++;
        if (accumCount == 2) {
            appendBitsToBuffer(accumData, 11, buf, &result.bitLength);
            accumData = 0;
            accumCount = 0;
        }
    }
    if (accumCount > 0) { // 1 character remaining
        appendBitsToBuffer(accumData, 6, buf, &result.bitLength);
    }
    assert(result.bitLength == bitLen);
    result.data = buf;
    return result;
}


// Public function - see documentation comment in header file.
struct qrcodegen_Segment qrcodegen_makeEci(long assignVal, uint8_t buf[])
{
    struct qrcodegen_Segment result;
    result.mode = qrcodegen_Mode_ECI;
    result.numChars = 0;
    result.bitLength = 0;
    if (0 <= assignVal && assignVal < (1 << 7)) {
        memset(buf, 0, 1 * sizeof(buf[0]));
        appendBitsToBuffer(assignVal, 8, buf, &result.bitLength);
    } else if ((1 << 7) <= assignVal && assignVal < (1 << 14)) {
        memset(buf, 0, 2 * sizeof(buf[0]));
        appendBitsToBuffer(2, 2, buf, &result.bitLength);
        appendBitsToBuffer(assignVal, 14, buf, &result.bitLength);
    } else if ((1 << 14) <= assignVal && assignVal < 1000000L) {
        memset(buf, 0, 3 * sizeof(buf[0]));
        appendBitsToBuffer(6, 3, buf, &result.bitLength);
        appendBitsToBuffer(assignVal >> 10, 11, buf, &result.bitLength);
        appendBitsToBuffer(assignVal & 0x3FF, 10, buf, &result.bitLength);
    } else {
        assert(false);
    }
    result.data = buf;
    return result;
}


// Public function - see documentation comment in header file.
bool qrcodegen_encodeSegments(const struct qrcodegen_Segment segs[], size_t len,
                              enum qrcodegen_Ecc ecl, uint8_t tempBuffer[], uint8_t qrcode[])
{
    return qrcodegen_encodeSegmentsAdvanced(segs, len, ecl,
                                            qrcodegen_VERSION_MIN, qrcodegen_VERSION_MAX, -1, true, tempBuffer, qrcode);
}


// Public function - see documentation comment in header file.
bool qrcodegen_encodeSegmentsAdvanced(const struct qrcodegen_Segment segs[], size_t len, enum qrcodegen_Ecc ecl,
                                      int minVersion, int maxVersion, int mask, bool boostEcl, uint8_t tempBuffer[], uint8_t qrcode[])
{

    assert(segs != NULL || len == 0);
    assert(qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX);
    assert(0 <= (int)ecl && (int)ecl <= 3 && -1 <= (int)mask && (int)mask <= 7);

    // Find the minimal version number to use
    int version, dataUsedBits;
    for (version = minVersion; ; version++) {
        int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;  // Number of data bits available
        dataUsedBits = getTotalBits(segs, len, version);
        if (dataUsedBits != -1 && dataUsedBits <= dataCapacityBits) {
            break;    // This version number is found to be suitable
        }
        if (version >= maxVersion) {  // All versions in the range could not fit the given data
            qrcode[0] = 0;  // Set size to invalid value for safety
            return false;
        }
    }
    assert(dataUsedBits != -1);

    // Increase the error correction level while the data still fits in the current version number
    for (int i = (int)qrcodegen_Ecc_MEDIUM; i <= (int)qrcodegen_Ecc_HIGH; i++) {
        if (boostEcl && dataUsedBits <= getNumDataCodewords(version, (enum qrcodegen_Ecc)i) * 8) {
            ecl = (enum qrcodegen_Ecc)i;
        }
    }

    // Create the data bit string by concatenating all segments
    int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;
    memset(qrcode, 0, qrcodegen_BUFFER_LEN_FOR_VERSION(version) * sizeof(qrcode[0]));
    int bitLen = 0;
    for (size_t i = 0; i < len; i++) {
        const struct qrcodegen_Segment *seg = &segs[i];
        unsigned int modeBits = 0;  // Dummy value
        switch (seg->mode) {
            case qrcodegen_Mode_NUMERIC     :
                modeBits = 0x1;
                break;
            case qrcodegen_Mode_ALPHANUMERIC:
                modeBits = 0x2;
                break;
            case qrcodegen_Mode_BYTE        :
                modeBits = 0x4;
                break;
            case qrcodegen_Mode_KANJI       :
                modeBits = 0x8;
                break;
            case qrcodegen_Mode_ECI         :
                modeBits = 0x7;
                break;
            default:
                assert(false);
        }
        appendBitsToBuffer(modeBits, 4, qrcode, &bitLen);
        appendBitsToBuffer(seg->numChars, numCharCountBits(seg->mode, version), qrcode, &bitLen);
        for (int j = 0; j < seg->bitLength; j++) {
            appendBitsToBuffer((seg->data[j >> 3] >> (7 - (j & 7))) & 1, 1, qrcode, &bitLen);
        }
    }

    // Add terminator and pad up to a byte if applicable
    int terminatorBits = dataCapacityBits - bitLen;
    if (terminatorBits > 4) {
        terminatorBits = 4;
    }
    appendBitsToBuffer(0, terminatorBits, qrcode, &bitLen);
    appendBitsToBuffer(0, (8 - bitLen % 8) % 8, qrcode, &bitLen);

    // Pad with alternate bytes until data capacity is reached
    for (uint8_t padByte = 0xEC; bitLen < dataCapacityBits; padByte ^= 0xEC ^ 0x11) {
        appendBitsToBuffer(padByte, 8, qrcode, &bitLen);
    }
    assert(bitLen % 8 == 0);

    // Draw function and data codeword modules
    appendErrorCorrection(qrcode, version, ecl, tempBuffer);
    initializeFunctionModules(version, qrcode);
    drawCodewords(tempBuffer, getNumRawDataModules(version) / 8, qrcode);
    drawWhiteFunctionModules(qrcode, version);
    initializeFunctionModules(version, tempBuffer);

    // Handle masking
    if (mask == qrcodegen_Mask_AUTO) {  // Automatically choose best mask
        long minPenalty = LONG_MAX;
        for (int i = 0; i < 8; i++) {
            drawFormatBits(ecl, (enum qrcodegen_Mask)i, qrcode);
            applyMask(tempBuffer, qrcode, (enum qrcodegen_Mask)i);
            long penalty = getPenaltyScore(qrcode);
            if (penalty < minPenalty) {
                mask = (enum qrcodegen_Mask)i;
                minPenalty = penalty;
            }
            applyMask(tempBuffer, qrcode, (enum qrcodegen_Mask)i);  // Undoes the mask due to XOR
        }
    }

    assert(0 <= (int)mask && (int)mask <= 7);
    drawFormatBits(ecl, mask, qrcode);
    applyMask(tempBuffer, qrcode, mask);

    return true;
}


// Returns the number of bits needed to encode the given list of segments at the given version.
// The result is in the range [0, 32767] if successful. Otherwise, -1 is returned if any segment
// has more characters than allowed by that segment's mode's character count field at the version,
// or if the actual answer exceeds INT16_MAX.
testable int getTotalBits(const struct qrcodegen_Segment segs[], size_t len, int version)
{
    assert(segs != NULL || len == 0);
    assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
    int result = 0;
    for (size_t i = 0; i < len; i++) {
        int numChars = segs[i].numChars;
        int bitLength = segs[i].bitLength;
        assert(0 <= numChars && numChars <= INT16_MAX);
        assert(0 <= bitLength && bitLength <= INT16_MAX);
        int ccbits = numCharCountBits(segs[i].mode, version);
        assert(0 <= ccbits && ccbits <= 16);
        // Fail if segment length value doesn't fit in the length field's bit-width
        if (numChars >= (1L << ccbits)) {
            return -1;
        }
        long temp = 4L + ccbits + bitLength;
        if (temp > INT16_MAX - result) {
            return -1;
        }
        result += temp;
    }
    assert(0 <= result && result <= INT16_MAX);
    return result;
}


// Returns the bit width of the segment character count field for the
// given mode at the given version number. The result is in the range [0, 16].
static int numCharCountBits(enum qrcodegen_Mode mode, int version)
{
    assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
    int i = -1;  // Dummy value
    if      ( 1 <= version && version <=  9) {
        i = 0;
    } else if (10 <= version && version <= 26) {
        i = 1;
    } else if (27 <= version && version <= 40) {
        i = 2;
    } else {
        assert(false);
    }

    switch (mode) {
        case qrcodegen_Mode_NUMERIC     : {
            static const int temp[] = {10, 12, 14};
            return temp[i];
        }
        case qrcodegen_Mode_ALPHANUMERIC: {
            static const int temp[] = { 9, 11, 13};
            return temp[i];
        }
        case qrcodegen_Mode_BYTE        : {
            static const int temp[] = { 8, 16, 16};
            return temp[i];
        }
        case qrcodegen_Mode_KANJI       : {
            static const int temp[] = { 8, 10, 12};
            return temp[i];
        }
        case qrcodegen_Mode_ECI         :
            return 0;
        default:
            assert(false);
    }
    return -1;  // Dummy value
}
